Current fuel systems for vehicles include a valve which opens and closes to allow vapor from the fuel tank to escape when the tank is being re-fueled. The vapor flows from the fuel tank, through the valve, and into a canister, where the vapor is stored until it is dispensed back into the intake of the engine. The valve is also able to provide relief of vacuum pressure that builds up in the fuel tank as the fuel levels decrease during operation of the vehicle. The valve also functions to seal the fuel tank between the fuel tank and the vapor storage canister.
The valve is typically operated using an actuation device, such as a solenoid, which is energized to open the valve, and hold the valve in an open position while the vehicle is being refueled. Current designs for solenoids used in these applications remain energized while the valve is opened during the time the vehicle is being re-fueled. This drains power from the battery, and reduces the overall efficiency of the vehicle. Additionally, the fuel tank, and the portion of the airflow system outside the fuel tank must be tested for leaks, so the airflow system must also be sealed with a valve on the fresh air side of the canister, such as a vent valve. These valves must also be tested to make sure they are functioning properly and that their positions (e.g. open or closed) may be verified, with minimal costs. This type of diagnostic testing may be required when the valves are first installed on a vehicle (during the manufacturing process or after repair), or after the battery has been disconnected.
Accordingly, there exists a need for a valve assembly which is able to remain in an open position while the vehicle is being re-fueled to allow vapors to flow out of the fuel tank, while at the same time minimizing the amount of energy used to maintain the valve in an open position. There is also a need for a valve assembly which meets current packaging requirements, and is capable of performing diagnostic tests to ensure that the valves are working correctly after installation, or after the battery has been disconnected.